In the earlier valves of the variety of Lewis U.S. Pat. No. 311,902, and including the Interstop and Metacon valves of today as exemplified by U.S. Pat. No. 4,063,668, the fixed and sliding refractory components are mortar bonded into metal components. The engineering philosophy is that during operation the refractory components are held in an abutting relationship as well as in vertical and lateral compression to prevent fracture of the refractory plates. Even if minor fracture occurs, the compression provided by the metal encasement is intended to avoid "break-out" of the liquid metal.
In the early sliding gate valves of the variety covered by the subject Shapland et al patent, springs are used to apply the abutting and vertical compression force. In such valve constructions, the stationary and sliding refractory plates are mortar bonded into light weight metal stampings which encase the refractory on all but the abutting faces. The metal encasement serves to assist in distributing the spring pressure of the bottom of the refractory plates and to contain the plates laterally. In some modification of this type of valve, a metal or combination metal and compressible refractory fiber plate is used to distribute the spring pressure over the bottom of the refractory. A band tensioned and clamped or a band welded and then shrunk around the periphery of the plates are used to contain and compress the refractory laterally.
With the valves of the prior art, and more particularly the refractory of the prior art, efforts have invariably been made to insure planarity of the faces of the refractory. Oftentimes this incurs expensive forming steps including the grinding of the faces. Furthermore, with the refractory encased in a metal container, even though perfect planarity may exist in the refractory, this can be impaired when a refractory is "mortared" into the metal container. In addition, when the refractories are contained or metal encased, oftentimes large sections of fired refractory are employed which are significantly more expensive than a monolithic type refractory which can be cast.
In the manufacture of steel, various elements of cost go into the price per ton. This includes the cost of operating sliding gate valves. It therefore becomes desirable to develop a sliding gate valve which maximizes the number of heats which the refractory can accommodate, minimizes the cost of the refractory, and utilizes the same in a valve construction at an omptimized investment cost. The amount of time the valve requires for change of refractory, the make-up time, and the inherent cost of the refractory must all be considered in addition to the safety of the valve in minimizing break-out.